Screening Assessment for the Challenge Quartz 14808-60-7
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Screening Assessment for the Challenge Quartz Chemical Abstracts Service Registry Number 14808-60-7 Cristobalite Chemical Abstracts Service Registry Number 14464-46-1 Environment Canada Health Canada June 2013 Screening Assessment CAS RN 14808-60-7, 14464-46-1 Synopsis Pursuant to section 74 of the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment of quartz, Chemical Abstracts Service Registry Number1 14808-60-7 and cristobalite, Chemical Abstracts Service Registry Number 14464-46-1. These substances were identified as a high priority for screening assessment and included in the Challenge initiative under the Chemicals Management Plan. Quartz and cristobalite were identified as high priorities as they were considered to pose greatest potential for exposure of individuals in Canada and their respirable forms are classified by the International Agency for Research on Cancer as carcinogenic to humans (quartz and cristobalite) and by the National Toxicology Program as known human carcinogens (crystalline silica). These substances met the ecological categorization criteria for persistence, but not for bioaccumulation potential or inherent toxicity to aquatic organisms. According to information reported under Section 71 of CEPA 1999 for the year 2006, over 10 000 000 kg of quartz were manufactured, imported and used in Canada. Based on the results of the same survey, over 10 000 000 kg of cristobalite were manufactured and between 1 000 000 and 10 000 000 kg were imported and used in the year 2006. It should be noted that this quantity does not represent the total quantities of quartz and cristobalite in the market in Canada because response to the mandatory section 71 Notice was required only if the substance or product, mixture or manufactured item containing the substance, was composed of more than 5% respirable crystalline silica and was intended for use within a residence. The major uses of quartz and cristobalite are in construction related activities such as road building and sanding in winter, and as a cement additive. Other uses include the manufacture of glass fibres and ceramics, as a filler and extender in rubber and coatings, and as an abrasive. Quartz and cristobalite are both naturally occurring. Quartz is found abundantly in many types of rock formations while cristobalite can be found in the ashes of volcanic eruptions. Cristobalite is less prevalent than quartz as its presence is limited to specific geographic regions and rock types. Quartz and cristobalite were qualitatively found to be very persistent because they are extremely resistant to chemical weathering. Also, quartz and cristobalite were qualitatively found to not bioaccumulate in aquatic organisms since they are expected to have very limited potential for uptake through for example the gill or gut of fish. Respirable fractions may physically accumulate in the lung tissues of terrestrial organisms. Results from available experimental toxicity studies indicate that quartz and cristobalite are not highly hazardous to aquatic organisms. In mammals however, these crystalline phases can cause harm to the lung (e.g., silicosis) depending on the severity 1 The Chemical Abstracts Service (CAS) Registry Number is the property of the American Chemical Society and any use or redistribution, except as required in supporting regulatory requirements and/or for reports to the government when the information and the reports are required by law or administrative policy, is not permitted without the prior, written permission of the American Chemical Society ii Screening Assessment CAS RN 14808-60-7, 14464-46-1 and duration of exposure. Quartz and cristobalite meet the criteria for persistence, but do not meet the criteria for bioaccumulation, as set out in the Persistence and Bioaccumulation Regulations. A risk quotient analysis at eight Canadian sites, integrating conservative to very conservative estimates of exposure via inhalation with a predicted no-effect concentration resulted in risk quotients below one, indicating the current estimated exposure concentrations of quartz and cristobalite in air are unlikely to cause harm to terrestrial fauna. On the basis of this evidence, it is concluded that these substances do not meet the criteria in paragraphs 64(a) and (b) of CEPA 1999, as they are not entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity or that constitute or may constitute a danger to the environment on which life depends. Concentrations of silicon in respirable particulate matter in Canada were identified and used to estimate inhalation exposure to quartz and cristobalite for the general population. The major anthropogenic releases of airborne respirable quartz and cristobalite are expected to come from dust generated due to agriculture, construction activity, and vehicle traffic on unpaved and paved roads. The International Agency for Research on Cancer (IARC) has classified respirable quartz and cristobalite from occupational exposure as Group 1 carcinogens (carcinogenic to humans). The U.S. National Toxicology Program classified crystalline silica of respirable size as known to be a human carcinogen. The basis for these classifications is sufficient evidence from human studies indicating a causal relationship between exposure to respirable crystalline silica in the workplace and increased lung cancer rates in workers. While the mode of induction of lung tumours is not fully elucidated, sufficient data exists to demonstrate that a threshold approach to risk characterization is appropriate. On the basis of the adequacy of the margins between conservative estimates of the exposure to quartz and cristobalite from ambient air and critical effect levels in experimental animals and humans, it is concluded that quartz and cristobalite do not meet the criteria in paragraph 64(c) of CEPA 1999, as they are not entering the environment in a quantity or concentration or under conditions that constitute or may constitute a danger in Canada to human life or health. Based on the information available, it is concluded that quartz and cristobalite do not meet any of the criteria set out in section 64 of CEPA 1999. These substances will be considered for inclusion in the Domestic Substances List inventory update initiative. In addition and where relevant, research and monitoring will support verification of assumptions used during the screening assessment. iii Screening Assessment CAS RN 14808-60-7, 14464-46-1 Introduction The Canadian Environmental Protection Act, 1999 (CEPA 1999) (Canada 1999) requires the Minister of the Environment and the Minister of Health to conduct screening assessments of substances that have met the categorization criteria set out in the Act to determine whether these substances present or may present a risk to the environment or to human health. Based on the information obtained through the categorization process, the Ministers identified a number of substances as high priorities for action. These include substances that • met all of the ecological categorization criteria, including persistence (P), bioaccumulation potential (B) and inherent toxicity to aquatic organisms (iT), and were believed to be in commerce in Canada; and/or • met the categorization criteria for greatest potential for exposure (GPE) or presented an intermediate potential for exposure (IPE) and had been identified as posing a high hazard to human health based on classifications by other national or international agencies for carcinogenicity, genotoxicity, developmental toxicity or reproductive toxicity. The Ministers therefore published a notice of intent in the Canada Gazette, Part I, on December 9, 2006 (Canada 2006), that challenged industry and other interested stakeholders to submit, within specified timelines, specific information that may be used to inform risk assessment, and to develop and benchmark best practices for the risk management and product stewardship of those substances identified as high priorities. The substances quartz and cristobalite were identified as high priorities for assessment of human health risk because they were considered to present GPE and had been classified by other agencies on the basis of carcinogenicity. The Challenges for these substances were published in the Canada Gazette on December 26, 2009 (Canada 2009a, 2009b). A substance profile was released at the same time. The substance profiles presented the technical information available prior to December 2005 that formed the basis for categorization of these substances. As a result of the Challenges, submissions of information pertaining to the substances were received. Although quartz and cristobalite were determined to be a high priority for assessment with respect to human health and also met the ecological categorization criteria for persistence, they did not meet the criteria for bioaccumulation or inherent toxicity to non- human organisms. Screening assessments focus on information critical to determining whether a substance meets the criteria as set out in section 64 of CEPA 1999. Screening assessments examine 1 Screening Assessment CAS RN 14808-60-7, 14464-46-1 scientific information and develop conclusions by incorporating a weight-of-evidence approach and precaution2. Quartz and cristobalite were grouped together in this screening assessment as they